The use of a plurality of shim stacks in double-piston arrangements is already known through British Patent Specification 2 202 921. The pistons or the piston arrangements can cooperate, in the inner positions of the pistons, with a constriction element (guide pin) which is arranged in the cylinder and with which the piston or the piston arrangement comes into cooperation so that the working medium is guided via a further shim stack, compared to the case where the pistons assume more outward positions relative to the shock absorber cylinder. By means of guiding the working medium between different numbers of shim stacks, the shock absorber has an automatically adjustable, position-dependent damping function which provides maximum damping in the innermost position of the pistons. When the pistons are not cooperating with the constriction element, the working medium is guided via a central recess in the piston arrangement. When the constriction element and the piston arrangement come into cooperation, the flow of the working medium is constricted in the central recess and the working medium is instead conveyed through the further shim stack. The constricting increases and is at its greatest, for example, in the absolute inner position of the pistons. The function described thus means that the rise in damping force increases the nearer the pistons are to the end position in relation to the constriction element, and vice versa.
To facilitate the description of the novel shock absorber hereinbelow, use is made of the expressions inner and outer positions of the piston arrangement. Inner positions are understood as meaning the piston positions where the piston arrangement has come into cooperation with the constriction element, and outer positions are to mean piston positions where the piston arrangement does not cooperate with the the constriction element.
In some cases it is necessary to be able to avoid using double-piston arrangements which make the shock absorber more complicated, with more parts and packings which are exposed to wear. Thus, making intervals between services and shock absorber replacements become relatively short compared to the case of a single-piston arrangement. The invention aims to solve these problems, among others.
There is also a requirement to provide different constructional possibilities with regard to the structure of the shock absorber and the manufacture of the shock absorber. The shock absorber manufacturer often desires different construction possibilities without running the risk of deviating from the fundamental principle, i.e. the use of shim stacks or the equivalent which are engaged and disengaged in different mutual positions between the piston and the cylinder. There is therefore a need for a modular concept in association with this type of shock absorber in which it is possible to incorporate the specific client requirements into a current shock absorber which can be characterized by small production series. The invention aims to solve this problem too.
It is also important, in this type of shock absorber, to be able to incorporate other types of devices acting on the working medium, for example devices acting on bleeding and damping force, which can be manual and/or sensor-controlled. It must be possible for this incorporation to be carried out with good accessibility and without affecting the control of the shim stacks or the equivalent. The invention also solves this problem.
In a double-piston arrangement, for example, there may be a requirement to effect two or more damping force adjustments, and this must be done in a manner which is not position-dependent. The invention solves this problem.